Elevators utilizing hydraulic pistons to raise and lower the elevator car have been in use for many years. Hydraulic piston elevators are best adapted for use in buildings having only a few floor levels since the piston shaft which lifts the elevator car must be of a length to raise the elevator to its maximum height. To accommodate the piston shaft a cylinder must be sunk in the ground beneath the building for the full length of the piston shaft. However, the cylinder must be installed in the ground so that it is parallel to vertical guide rails which align the elevator car in its travel within the building.
Hydraulic elevators as described above suffer serious degradation in performance if the piston cylinder is not accurately aligned with the guide rails. Misalignment can occur due to faulty installation or due to extended usage which can cause the guide rails to become misaligned with respect to the piston cylinder. Misalignment causes the sliding guides on the elevator car to bind the guide rails which in turn impedes the movement of the elevator car and can cause undesirable shaking and vibration. The misalignment becomes more exaggerated as the car travels further up in the building. In addition the misalignment can increase the wear on the machinery which in turn leads to increased service costs and decreased operational life time.
In U.S. Pat. No. 3,043,401 to Hellene there is disclosed a shackle spring mounting for hydraulic elevators. This mounting is designed to isolate the elevator car from vibration and to accommodate misalignment between the hydraulic cylinders and the elevator guide rails. However, it does not provide a rigid metal-to-metal contact between car and piston and in particular does not maintain such contact during misalignment between car and piston.
A need has thus arisen for a self-aligning elevator connection which will permit the elevator car to align with the guide rails in the elevator shaft while maintaining a secure connection to the hydraulic piston which lifts the elevator car. The connection must maintain positive metal contact between the elevator car and the piston and at the same time allow the elevator car to pivot to a limited extent about the top of the piston to accommodate any misalignment.